DE102019212405A1 - Method for determining an actual volume flow of a hydraulic actuating element of a gear shift element - Google Patents

Abstract

Method for determining an actual volume flow of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle with continuous filling and / or with continuous emptying of the hydraulic adjusting element, with the following steps: depositing an empirically determined pressure-volume characteristic curve (10) for the hydraulic actuator. Determining an actual pressure for the hydraulic actuator over time. Determination of an actual volume for the hydraulic actuator over time depending on the determined actual pressure and the stored pressure-volume characteristic curve (10). Determining the actual volume flow by deriving the determined actual volume over time.

Description

The invention relates to a method for determining an actual volume flow of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle. The invention also relates to a control device for carrying out the method.

A transmission of a motor vehicle has shift elements. To carry out a gear change or a shift in a transmission, at least one previously opened shift element must be closed and at least one previously closed shift element must be opened.

The shifting elements of a transmission can be frictional shifting elements, such as clutches or brakes, and positive shifting elements, such as claws.

To open and close a switching element, the respective switching element is actuated via a hydraulic actuating element, in particular via a hydraulic actuating piston that interacts with a valve. The actuation of a frictional switching element via a hydraulic actuator is subdivided into several phases, with sudden, discontinuous changes in the fill level of the hydraulic actuator being carried out in a so-called discrete phase, whereas in a continuous phase only non-sudden and therefore constant changes in the fill level of the actuator are permitted are.

When closing a frictional shifting element, the discrete phase of the hydraulic adjusting element is also referred to as discrete quick fill, whereas when opening a frictional shifting element, the discrete phase of the hydraulic adjusting element is also referred to as discrete quick emptying.

So far it has been difficult to reliably determine an actual volume flow of a hydraulic control element in the case of continuous filling and continuous emptying of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle. The actual volume flow of a hydraulic control element is the volume flow that flows through the hydraulic control element and the valve that interacts with the hydraulic control element. However, knowing the actual volume flow of a hydraulic adjusting element is important in particular to precisely regulate an actual position of the hydraulic adjusting element to a desired target position and to precisely set the torque transmitted or transferable by the switching element actuated via the hydraulic adjusting element.

From the DE 198 26 097 A1 a method is known with the aid of which a filling volume of a hydraulic adjusting element which actuates a frictional shifting element of a transmission can be corrected. A current load condition is determined from predetermined process variables of previous switching processes and a filling time is derived for the current load condition determined, which was previously determined by empirical preliminary tests.

There is accordingly a need to simply and reliably determine the actual volume flow of the hydraulic control element during continuous filling and continuous emptying of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle.

Proceeding from this, the invention is based on the object of creating a novel method for determining an actual volume flow of a hydraulic actuating element of a frictional shifting element transmission of a motor vehicle and a control device for carrying out the method.

This object is achieved by a method for determining an actual volume flow of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle according to claim 1.

The method according to the invention comprises the following steps: storing an empirically determined pressure-volume characteristic curve for the hydraulic adjusting element. Determining an actual pressure for the hydraulic actuator over time. Determining an actual volume for the hydraulic actuator over time depending on the determined actual pressure and the stored pressure-volume characteristic. Determining the actual volume flow by deriving the determined actual volume over time.

With the invention it is possible to exactly determine the actual volume flow of a hydraulic actuating element of a frictional shifting element such as a clutch or brake. For this purpose, the pressure-volume characteristic curve stored on the control side is accessed, which was previously determined empirically over time. On the basis of the actual pressure and the pressure-volume characteristic curve, an actual volume and thus an actual volume curve over time is determined, whereby the actual volume flow is determined simply and precisely by deriving this determined actual volume curve over time can be.

The stored pressure-volume characteristic curve is defined by a sensitivity point at which the frictional shifting element that can be actuated by the hydraulic control element begins to transmit torque, and by a base point at which the volume of the hydraulic control element is zero or approximately zero and the pressure of the hydraulic control element The actuating element corresponds to a preload pressure in the open basic position of the hydraulic actuating element, subdivided into several characteristic curve areas, a first characteristic curve range defining an interpolation range between an actuating element located at the base point and an actuating element filled up to the sensitivity point, and a second characteristic curve range defining a parameter range for one beyond the sensitivity point filled actuator defined.

The sensitivity point of the stored, empirically determined pressure-volume characteristic curve is adapted during operation, with offset values for the sensitivity pressure and the sensitivity volume being determined for the sensitivity point.

In the parameter area, the actual pressure is offset against the offset value for the sensitivity pressure to determine a corrected actual pressure, with an actual volume to be corrected being determined as a function of the corrected actual pressure and the stored pressure-volume characteristic curve, and with the The actual volume to be corrected is offset against the offset value for the sensitivity volume to determine the actual volume.

In the interpolation area, to determine the actual volume, the sensitivity volume offset with the offset value for the sensitivity volume is offset with a volume factor that is dependent on the actual pressure, base pressure and sensitivity pressure.

These features are used to precisely determine the actual volume flow, compensating for tolerances in gearbox production and compensating for aging of the gearbox during operation. For this purpose, the sensitivity point of the empirically determined pressure-volume characteristic curve is adapted, with the respective actual volume versus time and dependent on this, the actual volume depending on the offset values determined during the adaptation of the sensitivity point and depending on the characteristic range of the pressure-volume characteristic curve -Volume flow is determined.

The control device according to the invention for carrying out the method is defined in claim 10.

Preferred developments emerge from the subclaims and the following description.

• 1 eine exemplarische, empirisch ermittelte Druck-Volumen-Kennlinie für ein hydraulisches Stellelement eines reibschlüssigen Schaltelements eines Getriebes eines Kraftfahrzeugs.

Embodiments of the invention are explained in more detail with reference to the drawing, without being restricted thereto. It shows:

• 1 an exemplary, empirically determined pressure-volume characteristic curve for a hydraulic control element of a frictional shifting element of a transmission of a motor vehicle.

The invention relates to a method for determining an actual volume flow of a hydraulic actuating element of a frictional shifting element of a transmission of a motor vehicle with continuous filling and continuous emptying of the hydraulic actuating element.

The frictional shifting element, which is actuated by a hydraulic actuating element, can be a clutch or a brake of an automatic transmission, a converter lockup clutch of a converter of the transmission or a disconnecting clutch of the transmission.

In order to determine the actual volume flow of a hydraulic control element of a frictional shifting element of a transmission, an empirically determined pressure-volume characteristic curve for the hydraulic control element is stored in a control unit of the transmission. This pressure-volume characteristic, stored on the control side, is empirically determined by measuring a reference gear and then stored on the control side in the control unit of the respective gear.

During the operation of the transmission, an actual pressure for the hydraulic control element is determined over time. This time-dependent determination of the actual pressure for the hydraulic adjusting element can for example take place via a pressure sensor assigned to the hydraulic adjusting element. Alternatively, the actual pressure can also be calculated over time as a function of other variables known on the control side.

On the basis of the pressure-volume characteristic curve stored on the control side and depending on the determined actual pressure, an actual volume for the hydraulic actuator is determined over time in such a way that the determined actual pressure is used as an input variable for the pressure volume stored on the control side Characteristic curve is used, which then outputs the actual volume for the hydraulic actuator over time as the output variable. In this way, a time profile of the actual volume is determined.

In order to determine the actual volume flow of the hydraulic control element, the actual volume is derived over time.

1 shows an exemplary, empirically determined pressure-volume characteristic curve stored on the control side 10 , where the pressure p of a hydraulic control element is plotted against the volume V. The pressure-volume curve 10 is defined by at least two characteristic points, namely by a sensitivity point 11 as well as by a base point 12 .

At the sensitivity point 11 This is the point along the pressure-volume characteristic curve at which the frictional shifting element actuated by the hydraulic actuating element is just beginning to transmit moment, i.e. at which the frictional shifting element actuated by the hydraulic actuating element can be felt in the drive train of the motor vehicle.

The sensitivity point 11 the empirically determined pressure-volume characteristic curve stored on the control side 10 is according to 1 on the one hand through a sensitivity pressure p11 and on the other hand by a sensitivity volume V11 Are defined.

At the base point 12 the pressure-volume curve 10 it is the point at which the volume of the hydraulic adjusting element is zero or approximately zero and the pressure of the hydraulic adjusting element corresponds to a preload pressure in the open basic position of the hydraulic adjusting element.

The base point 12 is thereby through a base pressure p12 and a base volume V12 defined, where, as stated above, the base volume V12 Is zero and the base pressure p12 corresponds to the preload pressure in the open basic position of the hydraulic control element.

Preferably the base pressure p12 via an offset value Δp applied or applicable on the control side based on the sensitivity pressure p11 defined, where the base pressure p11 is lower than the sensitivity pressure by the applicable offset value Δp p11 . The following preferably applies: $$\text{p12}=\text{p11}-\mathrm{\Delta }\text{p}.$$

During the operation of the transmission, the sensitivity point is used, in particular, to compensate for manufacturing-related component tolerances and to compensate for age-related wear of the transmission 11 the empirically determined pressure-volume characteristic 10 adapted during operation, with this for the sensitivity point 11 Offset values are determined, namely an offset value OFp for the sensitivity pressure p11 and an offset value OFV for the sensitivity volume V11 .

To in the parameter area 14th the pressure-volume curve 10 To determine the actual volume, the determined actual pressure is offset against the offset value for the sensitivity pressure to determine a corrected actual pressure, with an actual volume to be corrected being dependent on the corrected actual pressure and the stored pressure volume -Curve 10 is determined, and the actual volume to be corrected is offset against the offset value for the sensitivity volume to determine the actual volume.

$${\text{V}}_{\text{IST-KORR}}={\text{f}}_{\text{P}-\text{V}}\left({\text{p}}_{\text{IST-KORR}}\right)$$

$${\text{V}}_{\text{IST}}={\text{V}}_{\text{IST-KORR}}+\text{OFV}$$

wobei
p_IST der Ist-Druck ist,
p_IST-KORR der korrigierte Ist-Druck ist,
OFp der Offsetwert für den Sensitivitätsdruck ist
V_IST-KORR das zu korrigierende Ist-Volumen ist,
f_P-V die Druck-Volumen-Kennlinie ist,
V_IST das Ist-Volumen ist,
OFV der Offsetwert für das Sensitivitätsvolumen ist.In parameter area14, the actual volume is determined using the following dependencies: $${\text{p}}_{\text{ACTUAL CORR}}={\text{p}}_{\text{IS}}-\text{OFp}$$

$${\text{V}}_{\text{ACTUAL CORR}}={\text{f}}_{\text{P}-\text{V}}\left({\text{p}}_{\text{ACTUAL CORR}}\right)$$

$${\text{V}}_{\text{IS}}={\text{V}}_{\text{ACTUAL CORR}}+\text{OFV}$$

in which
p _IS the actual pressure
p _{ACTUAL CORR is} the corrected actual pressure,
OFp is the offset value for the sensitivity pressure
V _{ACTUAL CORR is} the actual volume to be corrected,
f _{PV is} the pressure-volume curve,
V _{IS is} the actual volume,
OFV is the offset value for the sensitivity volume.

This determination of the actual volume in the parameter area14 takes place over time.

In the interpolation area 13 the pressure-volume curve 10 To determine the actual volume, the sensitivity volume offset with the offset value for the sensitivity volume is offset by a volume factor, namely multiplied, that of the actual pressure, base pressure p12 of the base point and sensitivity pressure p11 of the sensitivity point 11 is dependent.

$$\text{V}{11}_{\text{KORR}}=\text{V}11+\text{OFV}$$

$${\text{V}}_{\text{IST}}=\text{k}\ast \text{V}{11}_{\text{KORR}}$$

wobei
k der Volumenfaktor,
p_IST der Ist-Druck ist,
p11 der Sensitivitätsdruck ist,
p12 der Basisdruck ist,
V11_KORR das verrechnete Sensitivitätsvolumen ist,
V11 das Sensitivitätsvolumen ist,
OFV der Offsetwert für den Sensitivitätsdruck ist,
V_IST das Ist-Volumen ist.In the interpolation area 13 the actual volume is determined using the following dependencies: $$\text{k}=\left({\text{p}}_{\text{IS}}-\text{p}12\right)/\left(\text{p}11-\text{p}12\right)$$

$$\text{<figure-callout id="11" label="V" filenames="DE102019212405A1\_0015.png" state="{{state}}">V</figure-callout>}{11}_{\text{CORR}}=\text{<figure-callout id="11" label="V" filenames="DE102019212405A1\_0015.png" state="{{state}}">V</figure-callout>}11+\text{OFV}$$

$${\text{V}}_{\text{IS}}=\text{k}\ast \text{<figure-callout id="11" label="V" filenames="DE102019212405A1\_0015.png" state="{{state}}">V</figure-callout>}{11}_{\text{CORR}}$$

in which
k is the volume factor,
p _IS the actual pressure
p11 is the sensitivity pressure,
p12 is the base pressure,
V11 _{KORR is} the calculated sensitivity volume,
V11 is the sensitivity volume,
OFV is the offset value for the sensitivity pressure,
V _{IS is} the actual volume.

Also this determination of the actual volume in the interpolation area 13 again takes place over time.

wobei
V_IST das Ist-Volumen ist,
VS_IST der Ist-Volumenstrom ist,
d/dt das zeitliche Differential oder die Ableitung nach der Zeit ist.Using the in the above manner for the parameter area 14th and / or the interpolation area 13 determined actual volume curve over time, the actual volume flow can be determined by deriving it according to time, i.e. by forming the differentiation over time, where: $${\text{VS}}_{\text{IS}}=\text{d / dt}\left({\text{V}}_{\text{IS}}\right)$$

in which
V _{IS is} the actual volume,
VS _{IST is} the actual volume flow,
d / dt is the time differential or derivative with respect to time.

In the manner described above, the actual volume flow can be determined easily and precisely for a hydraulic adjusting element of a transmission, which is used to actuate a frictional shifting element of the transmission, namely during the continuous actuation of the hydraulic adjusting element.

The invention further relates to a control device for carrying out the method according to the invention, the control device being an electronic transmission control device. The control unit is set up to execute the method described above on the control side. The control unit is accordingly set up to determine an actual volume for the hydraulic actuator based on an empirically determined pressure-volume characteristic curve stored in the control unit and based on an actual pressure over time and by deriving the determined actual volume curve over time to determine the actual volume flow.

This above determination takes place over time, specifically at each sampling time of a sampling rate of the electronic control unit.

To carry out the method according to the invention, the electronic control device comprises hardware-based means and software-based means. The hardware-based means include data interfaces in order to exchange data with the assemblies involved in the execution of the method according to the invention, for example with a pressure sensor that provides the actual pressure. The hardware means also include a processor for data processing and a memory for data storage. The software-based means include program modules for carrying out the method according to the invention.

List of reference symbols

10

Pressure-volume characteristic

11

Sensitivity point

p11

Sensitivity point

V11

Sensitivity volume

12

Base point

p12

Base pressure

V12

Base volume

13

Interpolation area

14th

Parameter area

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 19826097 A1 [0007]

Claims (11)

Method for determining an actual volume flow rate of a hydraulic adjusting element of a frictional shifting element of a transmission of a motor vehicle with continuous filling and / or with continuous emptying of the hydraulic adjusting element, with the following steps: Storage of an empirically determined pressure-volume characteristic (10) for the hydraulic control element, Determining an actual pressure for the hydraulic actuator over time, Determination of an actual volume for the hydraulic actuator over time depending on the determined actual pressure and the stored pressure-volume characteristic curve (10), Determining the actual volume flow by deriving the determined actual volume over time. Procedure according to Claim 1 , characterized in that the pressure-volume characteristic curve (10) by a sensitivity point (11), at which the actuatable by the hydraulic adjusting element frictional shifting element begins to transmit torque, and by a base point (12) at which the volume of the hydraulic Control element is zero or approximately zero and the pressure of the hydraulic control element corresponds to a preload pressure in the open basic position of the hydraulic control element, is subdivided into several characteristic curve areas (13, 14), a first characteristic curve area an interpolation area (13) between a base point (12) located actuating element and an actuating element filled up to the sensitivity point (11), a second characteristic curve range defining a parameter range (14) for an actuating element filled beyond the sensitivity point (11). Procedure according to Claim 2 , characterized in that the sensitivity point (11) is defined by a sensitivity pressure (p11) and a sensitivity volume (V11). Procedure according to Claim 2 or 3 , characterized in that the base point (12) is defined by a base pressure (p12) and a base volume (V12), the base volume (V12) being zero and the base pressure (p12) corresponding to the pre-tensioning pressure in the open base position of the hydraulic actuator. Procedure according to Claim 4 , characterized in that the base pressure (p12) is lower than the sensitivity pressure (p11) by an applicable offset value (Δp). Method according to one of the Claims 2 to 5 , characterized in that the sensitivity point (11) of the stored, empirically determined pressure-volume characteristic curve (10) is adapted during operation, with offset values (OFp, OFV) for the sensitivity pressure (p11) and the for the sensitivity point (11) Sensitivity volume (V11) can be determined. Procedure according to Claim 6 , characterized in that in the parameter area (14) the actual pressure is offset against the offset value for the sensitivity pressure (OFp) to determine a corrected actual pressure, that furthermore an actual volume to be corrected is dependent on the corrected actual pressure and the stored Pressure-volume characteristic curve (10) is determined, and that the actual volume to be corrected is offset against the offset value (OFV) for the sensitivity volume in order to determine the actual volume. Procedure according to Claim 7 , characterized in that the actual volume is determined in the parameter area (14) using the following dependencies: $${\text{p}}_{\text{ACTUAL CORR}}={\text{p}}_{\text{IS}}-\text{OFp}$$

$${\text{V}}_{\text{ACTUAL CORR}}={\text{f}}_{\text{P}-\text{V}}\left({\text{p}}_{\text{ACTUAL CORR}}\right)$$

$${\text{V}}_{\text{IS}}={\text{V}}_{\text{ACTUAL CORR}}+\text{OFV}$$

where p _{IST is} the actual pressure, p _{IST-KORR is} the corrected actual pressure, OFp is the offset value for the sensitivity pressure, VIST-KORR is the actual volume to be corrected, f _{PV is} the pressure-volume characteristic, V _IST is the actual volume, OFV is the offset value for the sensitivity volume. Method according to one of the Claims 5 to 8th , characterized in that in the interpolation area (13) to determine the actual volume, the sensitivity _{volume (V11 KORR} ) calculated with the offset value (OFV) for the sensitivity volume is calculated with a volume factor (k) which is derived from the actual pressure (p _IST ) , Base pressure (p12) and sensitivity pressure (p11). Procedure according to Claim 9 , characterized in that the actual volume is determined in the interpolation area (13) using the following dependencies: $$\text{k}=\left({\text{p}}_{\text{IS}}-\text{p}12\right)/\left(\text{p}11-\text{p}12\right)$$

$$\text{V}{11}_{\text{CORR}}=\text{V}11+\text{OFV}$$

$${\text{V}}_{\text{IS}}=\text{k}*\text{V}{11}_{\text{CORR}}$$

where k is the volume factor p _IST the actual pressure, p11 is the sensitivity pressure, p12 is the base pressure, V11 _{KORR is} the calculated sensitivity volume, V11 is the sensitivity volume, OFV is the offset value for the sensitivity pressure, V _{IST is} the actual volume. Control unit of a motor vehicle, in particular transmission control unit of a transmission of the motor vehicle, characterized in that it is set up, the method according to one of the Claims 1 to 10 to be carried out on the control side.

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